1. Field of the Invention
The present invention relates to techniques for accessing channels in networks. More specifically, the present invention relates to dynamic channel-access protocols.
2. Related Art
Recent advances in networking technology have made it possible to support multiple voice-related applications, such as mobile smart phones and Voice over Wireless Internet Protocol (VoWIP) on individual networks. In the near future, these applications may be running on mobile stations concurrently with legacy data-centric applications. To support such integrated voice/data traffic in a network, the channel-access protocol in these systems needs to provide high channel utilization and bounded channel-access delay. The former is important for data-centric applications, and the latter is critical for providing uninterrupted data delivery in voice-related applications.
Contention-based channel-access schemes have previously been developed for ad-hoc networks and for wireless local area networks or LANs. However, these existing approaches are unable to provide high channel utilization as network load increases. In addition, ad-hoc networks that utilize such conventional channel-access schemes are vulnerable to collisions, which can potentially starve certain stations. As a consequence, the existing contention-based approaches are unable to ensure an upper bound on the channel-access delay.
‘Contention-free’ schemes have been proposed to overcome these limitations. These contention-free schemes use global and/or local topology information to produce deterministic transmission schedules that allow nodes in an ad-hoc network to periodically access the communication channel without collision and to also ensure a bounded channel-access delay. Unfortunately, these contention-free schemes typically require an excessive amount of control signaling overhead and may not be tolerant of topological changes.
Recently, randomized channel-access approaches have been proposed in an attempt address these additional challenges. These randomized schemes utilize probabilistic transmission schedules in which each device always has a certain probability to access the channel during a given data slot. While such approaches incur less control overhead than the earlier contention-free channel-access protocols, they still do not ensure a bound on channel-access delay.
Hence what is needed is a method and an apparatus that facilitates channel-access in networks without the problems listed above.